This invention relates to flip chip mounting methods, and in particular relates to flip chip mounting techniques that employ an insulating, adhesive film.
Various methods of conventional flip chip mounting are known. One representative example is the flip chip mounting technique using an insulating adhesive film. As opposed to other flip chip mounting methods, this technique has features which enable simplification of the mounting process, like bonding of an integrated circuit (IC) chip to a substrate such as a circuit board, and underfilling around the bonding point with a resin sealant.
This mounting technique has attracted attention recently, and in 1997 Japanese Public Patent Report No. 97815, Paragraphs [0018] and [0020] disclose a mounting technique where gold (Au) bumps on the IC chip are directly bonded to substrate electrodes; this method is referred to hereinafter as direct mounting. Also, Paragraph [0014] describes a mounting technique where Au bumps on the IC chip are indirectly bonded to substrate electrodes; this method is referred to hereinafter as indirect mounting.
However, with indirect mounting, electrical bonding of an IC chip and a substrate is achieved via a conductive adhesive layer which fills through-holes in an insulating adhesive film placed on both the chip and the board. In the direct mounting method, on the other hand, a mediating electrically conductive adhesive layer is not used, and bonding is achieved by bringing the Au bumps of the IC chip into contact with electrodes of the circuit board by inserting the bumps into through-holes pierced in the insulating adhesive film. Thus the indirect method has the problem of lower reliability than the direct method, as well as susceptibility to conductivity defects.
Therefore, although priority is being placed on direct mounting even in this case, the insulating adhesive film must have in it many minute through-holes that were, e.g., pierced, to enable insertion of the Au bumps of the chip through the holes; the processing requiring this technique can be troublesome and the method lacks general applicability.